SKF QJ311 N2MA/C3 Vierpunktlager (55x120x29)

As a four-point contact ball bearing, this bearing carries axial loads in both directions and moderate radial loads. The dynamic load rating of 127 kN characterises this bearing. The static load rating is 108 kN. The limiting speed is 10000 rpm. This variant features increased radial clearance (C3). This open version is intended for axially located shafts whose interference fit or heating noticeably reduces the mounted clearance.

In this version too the four-point contact ball bearing remains an axially carrying design: the gothic-arch raceways support longitudinal forces in both directions through a single ball row, while the radial load falls to an adjacent radial bearing. The difference lies in the clearance. In the four-point contact bearing it directly determines the contact angle at which the balls carry: increased clearance (C3) leads to a larger contact angle and therefore to greater axial and lower radial load-carrying action — so the clearance does not merely make the design more tolerant of fit and heating, it makes it axially more pronounced.

At the same time the larger initial play absorbs the reduction that follows from a tight inner ring seat and a temperature difference between the rings. The open form has no seal of its own; for the design, axial force, fit, temperature profile and the desired contact angle should be assessed together.